JPH01299770A - Output control method for gas shielded arc welding power source - Google Patents

Abstract

PURPOSE:To stabilize an arc at the early stage of arc generation and to prevent a droplet from being floated and scattered at the last stage of the arc by holding a welding current at a low level and then, increasing it to a high level during a short-circuit period of time and decreasing the welding voltage during an arc period of time. CONSTITUTION:During the arc period of time, since the welding voltage is controlled so as to be decreased, blazing-up of a consumable electrode immediately after the arc is generated is suppressed and the arc is stabilized by decreasing of the welding voltage and during the last stage of the arc, arc length is gradually shortened and the grown droplet is prevented from being floated and while the occurrence of spatters being suppressed, the transfer to the next short-circuit state is facilitated. Further, since the welding current is decreased from the set high level at the last stage of a short circuit by the decreasing rate determined inevitably by the decreased welding voltage and arc length, a flicker phenomenon is not generated and at the early stage of arc generation, the sufficient heat input is carried out on the consumable electrode and base metal to be welded by a high current value and the growth of the droplet and ununiformity of a weld base are solved and besides, the current value before and after the short-circuit transfer of the droplet is decreased and the droplet is prevented from being scattered and the occurrence of spatters is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention uses a gas shield to alternately generate a short circuit and an arc between a consumable electrode shielded by a shield gas and a welding base material. The present invention relates to an output control method for a gas shielded arc welding power source that controls the output of an arc welding power source.

[Conventional technology]

Generally, in gas shielded arc welding, Fig. 3(a) -
The process shown in (f) is repeated, first in Figure 3 (a).
), the droplet (G) grown at the tip of the consumable electrode (W) comes into contact with the molten pool CM) of the base metal, resulting in a short-circuit state, and the intermediate short-circuit process shown in (1)) of the same figure occurs. In this case, the droplet (G) and the molten pool CM) are surely in contact, and the same figure (C)
In the short-circuit final stage shown in Figure 2, the droplet (G) forms a molten pool ((5)
As the droplet (G) moves to the side, a constriction occurs in the droplet (G).

Furthermore, as shown in the peaks in Figure 3, the droplet (G) is torn off and an arc begins to occur, and in the middle stage of arc generation, as shown in Figure (e), the droplet reappears at the tip of the electrode (W). (G) grows, and as shown in FIG.

By the way, in such short-circuit transition type gas-shielded arc welding, a power source with constant voltage characteristics is conventionally used as the welding power source, and when this type of conventional welding power source is used, the welding current waveform is usually as shown in Figure 4. From the moment the droplet formed at the tip of the welding wire contacts the molten pool and short-circuits, the welding current continues to increase until the arc is generated again at an increase rate determined by the circuit time constant of the power supply, and the welding arc After this occurs again, the welding current decreases at a rate determined by the time constant until short circuit occurs again.

By the way, in the short-circuit transition type gas-shielded arc welding described above, a large amount of spatter is generated at the moment when the droplet grows large and tries to short-circuit with the molten pool of the base metal, and especially when the current at this time is high, a large amount of spatter is generated. It is well known that

Therefore, in order to suppress the amount of spatter generated, for example, Japanese Patent Laid-Open No. 60-183977 (B28K
As described in 9106), it has been considered to lower the average welding current before and after the short-circuit transfer of the droplet to the molten pool, and to control the output of the power supply fζ so that the droplet is not blown away by the repulsive energy of the arc. There is.

That is, the welding current waveform in this case becomes as shown in FIG. 5 or FIG. 6, and after the arc re-occurs from the short circuit, the consumption Fi! A high current period Tp is provided to form a droplet at the tip of the pole and to ensure penetration of the weld base metal. After this high current period, by the 9th short circuit, the droplet is A low current period Tb is provided to prevent the current from being blown away.

In addition, FIG. 5 shows the current waveform when the current value in the high current period Tp is constant current controlled to Ip, and FIG. 6 shows the current waveform in the high current period Tp.
This is a current waveform when the voltage value of p is constant voltage controlled to Vp, and in both Figures 5 and 6, the current value in the low current period 'rb is constant current controlled to Ib (<Ip).

[The problem that the invention attempts to solve]

However, in this case, if the welding target changes and the consumable electrode, welding base material, and shielding gas change, the arc period will fluctuate, causing a short circuit during the high current period, making the arc unstable, and spatter. This may increase the amount of arc generated, or the low current period may become too long, resulting in an uneven weld bead shape.In particular, fluctuations in the arc length due to changes in the condition of the weld zone in the welding base metal may cause the consumable electrode There is a problem in that the melting rate of the resin fluctuates, which promotes the occurrence of the above-mentioned disadvantages.

In addition, the flickering phenomenon of the arc light due to the difference in current value between the high current period and the low current period causes the weld bead to become uneven, which requires post-processing to correct the uneven weld bead. This results in a decrease in efficiency.

Therefore, the present invention has been made with the above-mentioned points in mind, and an object of the present invention is to reduce the amount of spatter generated and to form a beautiful and good weld bead.

[Means to solve the problem]

Next, in order to achieve the above object, the welding current flowing through the consumable electrode and the welding base metal, and the welding voltage between the consumable electrode and the base metal are controlled, and the welding voltage between the consumable electrode and the welding base metal shielded by a shielding gas is controlled. In the output control method of a gas-shielded arc welding power source that alternately generates a short circuit and an arc with the base metal, the present invention provides a method for controlling the output of a power source for gas shielded arc welding that alternately generates a short circuit and an arc with the base metal, wherein the welding current is initially maintained at a low level during the short circuit period, and then increased to a high level. The welding voltage is increased and during the arcing period, the welding voltage is decreased.

Further, during the arc period, the welding voltage may be initially decreased at a first rate of change, and then decreased at a second rate of change that is greater than the first rate of change.

[Effect]

Therefore, according to the present invention, since the welding voltage is controlled to decrease during the arc period, the reduction in the welding voltage suppresses the burning of the consumable electrode immediately after the arc occurs.
The arc is stabilized, and at the end of the arc, the arc length is gradually shortened to prevent the grown droplets from floating, and the transition to the 9th order short circuit state can be easily achieved while suppressing the occurrence of spatter.

Furthermore, since the welding current decreases from the high level set at the end of the short circuit at a rate of decrease that is inevitably determined by the welding voltage to be decreased and the arc length, there is no flicker phenomenon.
At the beginning of arc generation, the high current value allows sufficient heat input to the consumable electrode and the welding base metal, eliminating droplet growth and non-uniformity of the weld bead, and the current value before and after the short-circuit transition of the droplet By lowering the temperature, the scattering of droplets is prevented, and the generation of spatter is suppressed.

In addition, during the arc period, if the welding voltage is decreased at a first rate of change and then decreased at a second rate of change that is greater than the first rate of change, the stabilization of the arc at the early stage of arc generation, and the welding The effects of making the bead uniform and suppressing the amount of spatter generated at the end of the arc are even more pronounced, and even if the consumable electrode, welding base material, shielding gas, etc. change, the amount of spatter generated is reduced compared to the conventional method. A beautiful and good quality weld bead can be obtained.

〔Example〕

Next, the present invention will be explained in detail with reference to FIGS. 1 and 2 showing an embodiment thereof.

First, in Figure 1 showing the block configuration of the control circuit of a power supply for gas shielded arc welding, (2) smoothes the rectified output of the rectifier (1). (3) is a high frequency inverter section which is connected to the smoothing section (2) and consists of a switching element that converts the output DC of the smoothing section (2) into AC; (4) the output voltage of the JT inverter section (3) is A transformer that transforms, (5) an output side rectifier that rectifies the output AC on the secondary side of the transformer (4),
(6) is a power supply tip connected to one output terminal of the rectifier (5); (7) is a consumable electrode made of a welding wire that is energized through the power supply chip (6) and fed at a predetermined speed; (
The welding base metal connected to the other output terminal of the rectifier (5) via the DC detector (9), σq is an arc pressure detector, and the power supply tip (6) and the base metal (8 ) is detected.

α is the current setting device, (2) is the voltage setting device, Z is the error amplifier that derives the difference between the current detected value by the current detector (9) and the current setting value by the current setting device αη, and α4 is the voltage detector 1 An error term for deriving the difference between the voltage detected by the output device and the voltage setting value by the voltage setter (2), α9 is the voltage detector O
The consumable electrode (7) and the welding base material (8) are determined from the detected voltage by Q.
OQ is the first timer that operates for Ta time immediately after the occurrence of the short circuit, αη is the second timer that operates for Ta time immediately after the occurrence of the arc, (to) is the MPU, α A control signal based on the output signal of both error amplifiers (13, α4) is inputted to the inverter drive unit (MPU), and a switching signal is output to the switching element of the inverter unit (3). (
3) and also controls the output of the inverter section (3).

Now, when it is determined by the discriminator α9 that a short circuit has occurred, the first timer ae is activated by the output signal of the discriminator α9 to count the time Ta from the occurrence of the short circuit,
), during the above Ta time, the MPU (to) controls the inverter drive unit so that the welding current flowing between the narrow electrode (7) and the base metal (8) is at a low level Id. The output of the inverter section (3) is controlled, and after the Ta time has elapsed, as shown in FIG.
The MPU (
(to) controls the inverter drive unit α.

At this time, at the end of the short circuit, the welding current is at a low level I
d to a high level of Ia, the base metal (
Sufficient energy is given to the droplet at the tip of the electrode (7) that is in contact with the electrode (7), and the droplet is reliably transferred to the base material (8) without causing spatter, and the droplet is connected to the electrode (7). Base material (8)
The short circuit is broken and the arc re-occurs.

On the other hand, at the beginning of the short circuit, the welding voltage between the electrode (7) and the base metal (8) becomes almost zero, as shown in Fig. 2 (1)).
M so that the welding voltage increases slightly from the middle of the short circuit.
PUQ$ controls the inverter drive unit 0 theft, and after the Ta time has elapsed, the MPU (to)
The inverter drive unit α is controlled by.

Next, the droplet at the tip of the electrode (7) transfers to the base metal (8), an arc is generated again between the electrode (7) and the base metal (8), and the discriminator a9 determines that an arc has occurred. Then, in response to the output signal of the discriminator α9, the second timer αη is activated to count Ta time from the arc occurrence, and as shown in FIG. Va
MPU(t) decreases at a first rate of change θl from
After the inverter drive unit is controlled by
After a period of time elapses and until the ninth short circuit, the welding voltage remains at the first
The inverter drive unit Oe is controlled by the MPU (to) so that the inverter drive unit Oe is decreased at a second rate of change θ2 that is larger than the rate of change θl.

At this time, after the arc is generated, the welding voltage is decreased at the first rate of change θl without controlling it to a constant voltage for Ta time, thereby suppressing the burning of the electrode (7) and suppressing the arc length from increasing. This makes it possible to normalize the arc length early and stabilize the arc. Moreover, by decreasing the welding voltage at the second rate of change θ2 (>θ1) after the Ta time has elapsed, the arc length can be normalized at an early stage. When moving to the next short circuit period, the arc length can be gradually shortened to prevent the grown droplets from drifting, making it possible to easily transition to the next short circuit state.

In addition, after the arc is generated, the welding current is maintained at a high level Ia for the time Ta as shown in FIG. 2(a).
After the inverter drive unit a1 is controlled by the MPU (1119), after the Ta time elapses and until the 9th short circuit, the welding current decreases mainly due to the welding current reduction effect caused by the decrease in the welding voltage due to the second rate of change θ2. decrease.

In addition, after the Ta time elapses and until the 9th short circuit, in addition to reducing the welding rtt'% due to the decrease in the cross-contact voltage, the MPU (to) performs control to reduce the welding DC at a rate of change θ3. You can.

At this time, by maintaining the welding current at a high level Ia for Ta time after arc generation, sufficient heat input to the consumable electrode (7) and the base metal (8) can be ensured, and ), it is possible to sufficiently grow the droplet at the tip of the weld metal (8), prevent insufficient penetration of the base metal (8), and generate convection in the molten pool to float and release impurities inside the weld metal. , it becomes possible to obtain a beautiful weld bead.

Furthermore, by lowering the welding current before and after the droplet short-circuits and transfers to the base metal (8), it is possible to prevent the droplet from being blown away by the repulsive force of the arc, and to suppress the occurrence of spatter.

Then, as a consumable electrode, a YGW12 wire with a diameter of 1.2 mm according to JIS Z 8812 was used, the wire feeding speed was 8 m/min, and carbon dioxide gas was passed as a shielding gas at a flow rate of 2017 @. Under welding conditions, the waveform parameters of welding current and welding voltage are td = 50A, Ia = 40OA, Va = 27V, respectively.
Id=1.5m5ec, Ta==LQmsec, O
l = 0-04 V/ms e θ2 = 0, 17
When welding was performed with V/m5ec and θ3=0, the amount of spatter generated was 1.2 g/min, and welding was performed under the same welding conditions as above using a conventional welding power source with constant voltage output characteristics. ° Spatter generation fi7.2g/
The amount of spatter generated was significantly reduced compared to the previous model, and a uniform and beautiful weld bead was obtained.

Therefore, according to the above embodiment, during the arc period, the welding voltage is decreased for Ta time at the first rate of change θ1, and then decreased at the second rate of change θ2, which is larger than the first rate of change θ1. At the beginning of the arc, it is possible to stabilize the arc and make the weld bead uniform, and at the end of the arc,
It is possible to prevent the floating of droplets and the scattering of droplets, and it is possible to significantly reduce the amount of spatter generated compared to the conventional method.
A beautiful and good weld bead can be formed.

In addition, as another example, the welding voltage during the arc period may be controlled to decrease at a constant rate of change, and in this case, among the welding conditions in the above example, the wire feeding speed is 4 m/min. , each waveform parameter is I
d = 5 OA, I a = 800A, Va = 19
V, Td=1, 5m5ec, Ta=0, 01=
o * When welding was performed with θ2 = 0.17 V/m5ec and θB = 0, the amount of spatter generated was O,'1g1 min, which is the amount of spatter generated when using a welding power source with conventional constant voltage characteristics. Compared to the OgZ component, the amount of spatter was reduced, and the weld bead was uniform and beautiful.

In addition, when the optimum values of the above-mentioned welding voltage change rates θ1 and θ2 were found from actual welding results, 01Ei O~
0.15V/1nsec, θ2 is 0, 025~l
QV/m5ec is appropriate, and O
l and θ2 may be appropriately selected within these ranges.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

In gas-shielded arc welding, by reducing the welding voltage during the arc period, it is possible to stabilize the arc and make the weld bead uniform at the beginning of the arc, and at the end of the arc, it is possible to stabilize the arc and make the weld bead uniform. The scattering of droplets can be prevented, the amount of spatter generated can be significantly reduced compared to the conventional method, and a beautiful and good quality weld bead can be formed.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the output control method of the power source for gas shielded arc welding according to the present invention, FIG. 1 is a block diagram of the power source control circuit, and FIG. 2(a) is a block diagram of the power source control circuit. (b) is a waveform diagram of welding current and welding voltage, respectively.
Figures (a) to (f) are diagrams showing the process of droplet formation and transfer in gas-shielded arc welding, and Figures 4 to 6 are waveform diagrams of welding current in conventional examples, respectively. (7)...Consumable electrode, (8)...Welding base material.

Claims (2)

[Claims] (1) The welding current flowing through the consumable electrode and the welding base metal and the welding voltage between the consumable electrode and the base metal are controlled, and a short circuit occurs between the consumable electrode and the base metal that are shielded by shielding gas. In the output control method of a gas-shielded arc welding power source that alternately generates an arc and an arc, the welding current is initially held at a low level during the short circuit period, and then increased to a high level, and during the arc period, the welding voltage is decreased. A method for controlling the output of a power source for gas shielded arc welding, characterized in that: (2) The gas shield according to claim 1, wherein during the arc period, the welding voltage is initially decreased at a first rate of change, and then decreased at a second rate of change that is greater than the first rate of change. Output control method for arc welding power source.